This invention relates to the production of an article comprising cubic boron nitride (CBN) particles cemented to each other and bonded to a support layer, or substrate. Such composite articles find utility as wire drawing dies, tool inserts, abrasive bodies and wear surfaces. The preparation of the substrate alone for use as a wear surface is also contemplated.
High temperature, ultra high pressure preparation of tool inserts made of CBN crystals bonded to each other and bonded to and supported on a sintered carbide mass is described in U.S. Pat. No. 3,743,489--Wentorf et al. In the Wentorf et al. patent, particular aluminum alloys are employed as the bonding medium for the CBN crystals, not the substrate. The preparation of a metal-bonded CBN composite body containing greater than 70 percent by volume CBN and prepared at pressures at which CBN is metastable is disclosed in U.S. Pat. No. 3,982,911--Lee. The method described in the Lee patent requires placement of bonding material (i.e. certain aluminum alloys) on the side of the CBN particulates opposite from the substrate layer, an arrangement which presents a limitation on the geometry of the final composite structure. For example, it is very difficult to prepare a wire drawing die by the methods in the Lee patent.
The aforementioned restriction on bonding material placement has since been removed by the development of the process described in U.S. patent application Ser. No. 217,271--Lee et al., filed Dec. 17, 1980 and assigned to the assignee of the instant invention. The product produced by the Lee et al. invention comprises a cemented diamond mass bonded to a body of silicon-silicon carbide composite material. The silicon-silicon carbide composite initially serves as a source of silicon for the bonding, or cementing, of the diamonds and subsequently provides for the structural stability of the article itself as its substrate. The above-mentioned patents and application are incorporated by reference.